Introduction: This Worksheet Discusses Material Covered in the Fourth and Fifth Lectures

Introduction: This worksheet discusses material covered in the fourth and fifth lectures (01/18/17 and 01/20/2017). Chapter 9 examines these topics.

Concepts

1. Chemistry of replication.
2. Replication initiation.

Material

1. Chemistry of replication.

In this section, we’ll be examining important structural aspects of double-stranded DNA and how it affects replication.

1. What aspect of double-stranded DNA would you look to in order to predict at what temperature the strands will separate?

1. Explain what is meant by semi-conservative replication. How does conservative replication differ?

1. Below is a diagram of a double-stranded DNA molecule replicating. Give names to each of the strands below along with any pertinent descriptors. Indicate the direction of all strands.Indicate replication fork(s).

** Adapted from: ** Not an original image.

1. Why do Okazaki fragments form?

1. How many origins of replication do bacteria have? Eukaryotes? How many replicons each?

1. What does antiparallel mean in the context of DNA molecules?

1. How do new bases get added?

1. Proteins involved in replication.

We will focus on bacterial replication here, but will make distinctions about eukaryotic replication where necessary. We’ll attempt to get at the purpose of all enzymes involved, but the enzymes listed here are memorization material.

1. Describe what the initiator protein complex does. Why invest energy in so many proteins when double-stranded DNA naturally fluctuates into single-stranded forms?

1. Describe the proteins that are involved in making and maintaining the replication forks.

1. DNA primase, DNA polymerase I, and DNA polymerase III all add nucleotides, but what is the difference between them? Why are all necessary?

1. What would happen without DNA ligase?

1. DNA maintenance.

In this section, we’ll look at licensing, cell cycle checkpoints, and telomeres.

1. Why is it important for licensing factors to attach before replication in eukaryotic cells?

1. If a cell skips past the S-phase checkpoint and immediately replicates, what might happen to the resulting cells?

1. Describe the end-replication problem in eukaryotes.

1. What would happen if the RNA sequence in telomerase wasn’t a repeat? E.g. a normal sequence may be UAACCCUAACCC, but the non-repeat is UAACCCUAACGC.

1. Why don’t prokaryotes have licensing factors or express telomerase?

Things to do next

• Focus your review on things that were difficult from this worksheet. If it was really challenging, don’t worry; these are meant to be tough and push your understanding of the topics we covered.
• Memorization is unfortunately key for the replication proteins. Their functions shouldn’t be too conceptually difficult at this point, but you’ll have to make sure you have a good understanding of the order they act in.
• If you have any questions, ask me in session, in class, or by email. I’m more than happy to help.
• Next session (Thursday 01/26/17) we’ll be talking about any material not completed from this worksheet and about material from the sixth and seventh lectures (01/23/17 and 01/25/17). We won’t be able to discuss the eighth lecture specifically in a session.